The neuromuscular assessment of children is uniquely challenging. Unlike examination of the heart or lung, the complete bedside assessment of the neuromuscular system requires the active participation of the child and results must be evaluated in the context of normal child development and degree of cooperation. Moreover, neuromuscular disease severity is highly variable and progression, if present, is typically very slow. This impacts not only diagnosis, but also assessment of therapy. Indeed, clinical therapeutic trials and regular patient care may require children to undergo invasive or inconvenient tests, including muscle biopsy, magnetic resonance imaging and electromyography. A sensitive, noninvasive test to detect and measure neuromuscular pathology in children would greatly improve the ability to evaluate new therapies as well as to assist in the regular care of children suffering from these conditions. Electrical impedance myography (EIM) is one technique that may be especially useful in this regard. In EIM, an imperceptible high-frequency electrical current is applied via surface electrodes to a muscle or muscle group of interest and alterations in the consequent surface voltage pattern are measured. Alterations in the surface voltage patterns provide information on disease status and can track change over time. Convergence Medical Devices, Inc. is a small business whose main interest is in the commercialization of devices for the rapid application of EIM. In this applicatin, Convergence plans to build upon its success in its Phase 1 SBIR by further refining EIM technology for application to a pediatric population. We will achieve this by teaming up with several well- respected pediatric neuromuscular researchers across the country to further refine and test our system through four specific aims. In Specific Aim 1, we will obtain normative data on multiple muscles in 256 boys and girls aged 0-18 years and develop a user-friendly scoring system based on the percent predicted normal (akin that performed for pulmonary function testing). In Specific Aim 2, with the input of several experts, we will improve our software to incorporate these scores aiming to create a straightforward user interface. In Specific Aims 3 and 4, we will test our improved system in one of the most common and devastating neuromuscular diseases of childhood: Duchenne muscular dystrophy (DMD). We will first validate several optimized EIM scores that effectively track disease status in 5-12 year-old children over 1-year in whom functional measures can generally be accurately obtained. We will then evaluate the success of these EIM scores in their ability to detect disease progression over 3- and 6-month periods of time in DMD boys as compared to 3 groups of healthy boys: 0-4 years, 5-12 years, and 13-18 years of age. In addition to further refining pediatric EIM, we will also create innovative shared resources, including an online calculator to assist with EIM sample size calculations and an open-source online database of normal and DMD data which can serve as a foundation for future shared pediatric neuromuscular disease resources to both academic and industry investigators alike.